Back up your sierra\swat4\content\system\user.ini and sierra\swat4\contentexpansion\system\user.ini files if you like your keybinds and custom controls.

Go to Add & Remove programs (via control centre if necessary). Uninstall all mods, maps, skins, e.t.c. you may have listed for SWAT4/SWAT4:TSS. Uninstall SWAT4:TSS, check the box to remove the entire directory, uninstall SWAT4, check the box to remove the entire directory.

Run game, tested training mission, hit excape, abort, quit, 'yes' to quit towindows. Note: That the game took a VERY long time to start up as it did it'sfirst run chores. Very long for a 3.0Ghz/2GB system.